1. Field of the Invention
The present invention relates to an ignition coil apparatus for an internal combustion engine which applies a high voltage for generation of a spark discharge to a spark plug for each engine cylinder.
2. Description of the Related Art
As a conventional mounting structure for an ignition coil apparatus for an internal combustion engine, there has been known one in which a coil case with a part of a core received therein has a thick wall portion protruding toward an internal combustion engine side, and the internal combustion engine has a rotation limiting protrusion that limits or restricts the rotation of the ignition coil apparatus in the same direction as that in which a bolt engaged with the thick wall portion is able to rotate (see, for example, a first patent document: Japanese patent application laid-open No. 2002-48043 (claim 7)).
That is, the bolt is inserted into a through hole formed in the core which is located outside the coil case, so that the rotation of the ignition coil apparatus upon tightening the core against a mounting seat is prevented by the engagement of the rotation limiting protrusion with the thick wall portion.
In the mounting structure of the conventional ignition coil apparatus for an internal combustion engine, in order to limit or restrict the rotation of the ignition coil apparatus upon mounting thereof on the internal combustion engine, it is necessary for a head cover of the internal combustion engine to provide with a special protrusion structure, which deteriorates workability or working efficiency of the head cover, thus posing a problem that the cost of manufacture becomes high.